Arrangement for air conditioning control in buildings

ABSTRACT

Air condition control for buildings, having a roof structure of roof trusses relatively widely spaced, between which self-supporting roof plates are laid and covered by a covering layer so that a gap is formed between the covering layer and the roof plates. Air is passed in one or the other direction through a ventilation opening in the roof, through the air gap (13) and through ducts (9) in the roof plates. Air sucked in from the atmosphere through the ventilation opening passes through the ducts to an air conditioning unit (5) and to a distribution device (6) to maintain a suitable temperature in the building. Air flow can also be inverted by being supplied in the form of outdoor air to the air conditioning unit (5) and after its passage through the building being conducted away into the atmosphere through the roof structure by the ventilation opening.

FIELD OF THE INVENTION

This invention relates to an arrangement for controlling the aircondition in buildings, wherein the roof comprises plates withsubstantial mass which are self-supporting with a relatively wide span,and a covering layer laid on the outside of the roof plates, betweenwhich layer and plates a gap for air exchange with the atmosphere islocated and air is passed therethrough.

DESCRIPTION OF THE PRIOR ART

Co-operation between the carrying building structure and ventilationinstallations heretofore has been utilized to a relatively limitedextent for controlling the air condition in a building. Some examples,however, of such integration do exist. Roofs of hall buildings, forexample, comprise plates, which are assembled of concrete elements withTT-shaped cross-section and cover long spans. It was found that suchconcrete roofs, owing to the relatively high heat capacity of concrete,during successive warm summer's days yield air conditions, which aresubstantially better than those yielded by roofs of a lighter weightwith corresponding insulation. In winter-time also certain savings inenergy could be obtained. An improved roof construction of this kindimplies, that the concrete plate is provided with a covering layer ofsheet metal instead of asphalt roofing felt and the like. Such aconcrete-sheet metal roof renders possible ventilation of the air gapbetween insulation and covering layer and thereby offers specialadvantages.

In connection with the use of precast elements for multi-storeybuildings, floor elements with longitudinal holes have been utilized forbranching the ventilation system. At a specific design of such floors,the heat storage capacity in the hollow floor has been utilizedsystematically in such a manner, that in summer-time the cool night aircan be used for cooling the building on warm days and that inwinter-time excess heat produced during the day can be stored forheating purposes during nights and holidays.

A closely related development refers to so-called exhaust air windows,where the transmission losses of heat are reduced by windows acting assolar collectors. The warm air from the windows is passed into thebuilding, and consideration was made of the possibility of storing thisheat in the building structure, for example in the floors.

BRIEF SUMMARY OF THE INVENTION

The present invention, relates to buildings, the roof constructions ofwhich, briefly, comprise roof trusses, which are arranged withrelatively widely spaced relationship and between which self-supportingroof plates are located. The roof plates are covered by a covering layerin such a manner, that a gap is formed between the covering layer andthe roof plates. The invention is particularly suitable for industrialbuildings. According to the invention air is passed in one or the otherdirection through ducts provided in the roof. When the air is sucked infrom the atmosphere through ventilation cowls and passes through saidmeans, the air is led to an air conditioning unit and to a distributiondevice of some kind within the building for the purpose of maintaining asuitable temperature in the building. The air can also be led in theinverted direction and, thus, be taken up in the form of outdoor air bythe air conditioning unit and after having been passed through thebuilding be conducted away through the roof structure into theatmosphere by the ventilation cowls.

The invention, comprises an arrangement which is characterized in thatthe plates are formed with ducts, which at one end have an opening,which is connected both to the air conditioning unit and to intakes fromthe building and which has one or more upward connections to the air gaplocated thereabove. Several plates can be arranged one after the other,and the ducts can be connected by suitable pass-over means, which mayhave openings in connection with the air gap. Especially suitable areroof plates of concrete with TT-shaped cross-section, in which the ductsare laid in the beam webs. The covering layer in this design preferablyconsists of corrugated sheet metal, which is laid spaced from the uppersurface of the plate so that a gap is formed.

By applying a number of operation cases to the ventilation of abuilding, substantial technical effects with respect to the aircondition and especially to energy economy in the building can beachieved.

When the ventilation air is sucked in from the air gap into the ducts ofthe roof plates, the effects related below can be obtained.

Heat is recovered on occasions when the sheet metal roof acts as a solarcollector.

Transmission heat (leakage heat) through the insulation to the gapbeneath the covering layer is returned into the building. The excessheat in the air in the upper part of the building which is substantialat great room heights, is supplied to the roof plates through heattransmission and is recovered by the ventilation air flowing through theducts. The roof framing acts here as a heat exchanger.

Due to the heat taken out with ventilation air in the ducts of the roofframing, the air temperature in the upper part of the building islowered. The temperature difference between indoor and outdoor airdecreases, and the total heat transmission losses through the roofdecrease.

Owing to the possibility of positioning the connecting openings throughthe insulation between the air gap and the ducts in the roof plates(cold zones) in connection with the necessary supports for the proppedcovering layer, the thermal bridge effect of the openings is reducedsubstantially.

When the roof is covered with snow, the gap ventilation prevents thesnow from melting at the covering layer as long as the outdoortemperature is below 0° C., whereby the insulating capacity of the snowlayer is utilized, while the melting is accelerated when the outdoortemperature is higher than 0° C., so that the roof plate is exposed morerapidly and can act as a solar collector.

Ventilation through the gap eliminates the risks of moisture damage tothe insulation by leakage water through the covering layer or bycondensation in the gap space.

The temperature variations, and thereby the movements in the coveringlayer (roof metal sheet) are reduced because the layer is cooled by theair flow.

The heat accumulation capacity of the roof plates can be utilized fortime-shifted heaing with periodic excess heat or cooling of the roomduring day-time with cold accumulated during the night.

The roof plates can be cooled efficiently with the ventilation air inthe event of fire, so that the resistance against fire is increasedsubstantially.

The effects of unintentional ventilation by leaks in the roof areeliminated, in that such ventilation is caught in the gap.

When ventilation air instead is supplied to the gap from the hollowducts, i.e. when the system is used contrary to the direction describedabove, the effects related below can be obtained.

The roof framing can be cooled with outdoor air from the ducts and anair conditioning unit during warm summer-days.

This also brings about a substantial temperature decrease in the airgap, so that the covering layer (roof metal sheet) is cooled and extremetemperature movements in the covering layer are prevented when the roofis exposed to solar radiation on warm summer-days.

When outlets for the ventilation air are positioned at ridges in theform of separate fans, an added natural ventilation effect is achieved.

Due to the lowered temperature in the air gap, the inward heat leakagethrough the insulation in warm weather is reduced substantially.

In the case when the roof plates consist of TT-shaped concrete sections,the following degrees of freedom, which are essential for a cold roof,are obtained:

1. Roof openings with sufficient width for smoke lids, roof units etc.can be positioned substantially in any place between the carrying beamsof the TT-concrete plate, irrespective of whether it is carried outduring the manufacturing process, at the assembly of the building or atits conversion. These recesses can be made without requiring theTT-concrete plate to be lintelled.

2. The width of the plate can be varied for single elements withnon-modular length or width without giving rise to disturbing productiondifficulties.

3. Sound-insulating slabs can be mounted between the beam portions ofthe TT-concrete plates without thereby appreciably obstructing heatexchange with the indoor air at the roof level.

It can be suitable at times not to use certain of the hollow ducts inthe roof plates. This may apply, for example, to hollow ducts neargutters adjacent a facade, because hereby the gutter will not be cooledso much that the water freezes and locks the gutter with the knownconsequences resulting therefrom.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in greater detail hereinafter with referenceto the accompanying drawings. The description refers to a roofconstruction where the roof plates consist of concrete elements,so-called TT-concrete plates, which are covered with corrugated sheetmetal. The invention, however, must not be regarded as restricted to theembodiment described, because other sectional configurations of concreteelements and also forms of roof plates other than concrete elements andcovering layers other than corrugated sheet metal may be used.

FIG. 1 is a perspective, schematic view of a concrete structure for anindustrial building with several aisles and with a roof structure forutilizing the invention,

FIG. 2 is a portion of a longitudinal cross-sectional view on anenlarged scale through the roof structure taken along line II--II inFIG. 1,

FIG. 3 is a portion of a cross-sectional view on an enlarged scale takenalong the line III--III in FIG. 1,

FIG. 4 is a cross-sectional view on an enlarged scale taken along theline IV--IV in FIG. 2,

FIG. 5 is a portion of a longitudinal cross-sectional view showing aTT-concrete roof plate arranged according to the invention similar toFIG. 2 and on a larger scale,

FIG. 6 is a flow-sheet for an operation case 1 according to theinvention,

FIG. 7 is a flow-sheet shown in the same way for an operation case 2,

FIG. 8 is a flow-sheet for an operation case 3,

FIG. 9 is a flow-sheet for an operation case 4, and

FIG. 10 shows a modified roof shape in accordance with the invention.

DETAILED DESCRIPTION

In FIG. 1 a building constructed according to the present invention isshown schematically and perspectively. The roof of the building isindicated only schematically, in that the roof trusses 1 are shown andsupported in a conventional manner. With reference to FIG. 1, theinvention, briefly, can be explained as follows. Between an outercovering layer of corrugated sheet metal and the roof in the form ofconcrete elements a gap is located. In the roof plates, i.e. concreteelements, ducts extend in the direction tranversely to the rooftrusses 1. The ducts are indicated in FIG. 1 by the arrows 2. The dots 3indicate openings from the gap downward to the ducts. All ducts openinto a main pipe 4, which then extends to an air conditioning unit 5.From said unit extend conduit connections to supply-air terminal devices6, for example of low-impulse type, which are located downwardly in thebuilding and supply the building with conditioned air for heating andventilation.

In FIG. 2, which is a longitudinal section on an enlarged scale alongthe line II--II in FIG. 1, can be seen how the roof plates 7 are laidbetween the roof trusses 1. The arrows 2 are the same as in FIG. 1 andindicate the air flow through ducts 9 formed in the beam webs 8 of theroof plates. As appears from the Figure, connection exists between twoplates 7 located one after the other, which connection is indicated bythe reference numeral 10. Said connection implies a connecting device,which is located above the plates 7 and in the insulation 11 laid abovethe plates. The pass-over devices 10 have an opening 12, which opensinto the gap 13 laid between the roof plate 7 and the covering layer 14in the form of a corrugated metal sheet. FIG. 2 illustrates how thepass-over devices 10 are positioned at each roof truss 1, and eachpass-over device has an opening 12 at said gap. It is also to bementioned, that the gap is located between the insulation 11 and thelower surface of the covering layer 14. The arrows 2, thus, indicate theair flowing through the ducts in the roof plates, and the arrows 15indicate the air flowing in said gap.

FIG. 3 is a section along the line III--III in FIG. 1, where theleft-hand portion of the Figure shows the wall 36 of the building whichsupports the gutter valley 37 and the roof plate 7. The ducts 9 extendthrough the beam webs 8 of the roof plates 7. Above the roof plates 7the insulation 11 is located, and between the insulation 11 and thecovering layer extends the gap 13. As can be seen, the right-hand one ofthe two ducts 9 includes a pipe connection 16, which extends downward tothe duct 9 from the gap 13. In addition to the connection 12 shown inFIG. 2, thus, further connecting places are located between the gap 13and the ducts 9. The connecting places preferably shall be sodistributed that a uniform flow condition for air from the gap 13 to theducts 9, or vice versa, is obtained. Furthermore, a certain number ofsealings (not shown) preferably can be inserted with certain spacedrelationship between the covering layer and the roof plate transverselyto the roof trusses. Said sealings guide the flow of the air in the gap13, and a suitable distribution of the air flow can be obtained.

FIG. 4 is a section along the line IV--IV in FIG. 2 and differs from thesection according to FIG. 3 only in that the scale is slightly greaterand the longitudinal extension of the section is shortened. In FIG. 4can be seen both the duct 9 in the roof plate and the connecting pipe 16from the gap 13 to the duct 9. The arrows 15 indicate the air flow fromthe gap 13 into the downward pipe 16. According to the right-hand arrow15, the air flows over an attachment bar 17, which carries the coveringlayer in the form of the corrugated sheet 14. Where said bar abuts thelower corrugations, a passage exists in the wave troughs above the bar17. This prevents or eliminates a thermal bridge arising via the bar 17from the corrugated metal sheet 14. The opening 12 of the pass-overdevice 10 can open into a distribution pipe (not shown) on the bar 17which distributes the air upward along the lower surface of the metalsheet.

FIG. 5 is a sectional view similar to FIG. 2 showing a TT-concrete roofplate, which is provided with beam webs 18 suitably distributed andextending between the roof trusses 1. The roof plates hereby areself-supporting. The beam webs 18 include the aforementioned ducts 9,and two different embodiments of the pass-over devices 10 are shown. Inthe left-hand embodiment the pass-over device is fork-shape with twolegs of equal length. The opening 12 to the gap 13, thus, is locatedsymmetrically relative to the legs. In the right-hand embodiment theopening 12 is located directly in front of one of the legs in thepass-over devices 10. Thus, the pass-over devices 10 act to transfer airfrom the ducts 9 in one plate to corresponding ducts 9 in an adjacentplate and to take in or remove air from the gap 13.

In the following, four operation cases are described with reference toFIGS. 6-9, which schematically illustrate the air flow. Thicker linesindicate that air flow takes place. The numeral 21 refers to theschematically shown cross-section of the roof structure described above,5 designates the aforementioned air conditioning unit, 22 designates aventilation cowl on the ridge, and 23 is a fan for outdoor air intake.The operation case illustrated in FIG. 6 is applied during day-time aslong as the temperature v₁ in the main duct to the air conditioning unit5 during day-time is lower than or equal to the desired supply-airtemperature v₂ after the air conditioning unit. The air is passed fromthe air conditioning unit in a suitable way, for example via supply-airterminal devices 6 (see FIG. 1), to the interior of the building. Theoutdoor air being used, thus, is the air which flows through theventilation cowls 22 according to the arrows 24. The fan 23 can suck inair through the opening 25, but as mentioned it is not the case in theoperation case 1. Through a conduit 26, furthermore, return air can flowout into the ambient atmosphere. Said conduit 26 is closed in thisoperation case 1.

As regards operation case 2, see FIG. 7. When the temperature v₁ exceedsthe desired supply-air temperature v₂, the operation case according toFIG. 7 arises, in which a mixture of outdoor air is supplied to the airconditioning unit 5 via the ventilation cowls 22 and a direct inlet. Inthis connection is to be added, that the operation case 1 is limitedthereto by a lowest acceptable temperature on the inner surface of theroof. This lowest temperature can be limited, for example, by the riskof condensate precipitation on the inner surface of the roof or by alower comfort limit for human beings with respect to radiation cooling.

As regards operation case 3, see FIG. 8. The operation case 3 is appliedin night-time after a day with the operation cases 1 and 2. It isapparent from this Figure that then only a circulation takes placethrough the building and the air conditioning unit 5, in that the returnair from the interior of the building is taken in at the conduit 26, andits temperature is maintained in the air conditioning unit 5. Throughthe roof construction 21 only ventilation by natural draught takes placeby means of the ventilation cowls 22. This is indicated by the arrows24. No outdoor air is taken in via the conduit 27, and the operationcase 3 presupposes that no appreciable activity occurs in the buildingduring night-time.

As regards operation case 4, see FIG. 9. In this operation case theoutdoor air is supplied directly via the conduit 27 to the airconditioning unit 5 where its temperature is determined, and the airthen is supplied to the building. The return air from the interior ofthe building flows into the conduit 26 and is passed on to the roofconstruction 21 by overpressure in the building and by means of draughtfrom the ventilation cowls 22. Outdoor air can be supplied directly viathe conduit 25 to the roof structure. The operation case 4 is actuatedwhen the amount of outdoor air from the roof structure 21, i.e. the airgap and the hollow ducts of the roof framing, decreases to zero. Thisoperation case is applied also at night-time or such day ending with theoperation case 2. At the time of return to day operation on thefollowing day, the temperature difference between the exhaust air fromthe roof and the outdoor air temperature is sensed. When thistemperature difference falls below a certain value, operation case 2 isapplied. Otherwise operation case 4 is continued. It is to be observedthat said temperature is decisive for the operation cases and saidtemperature differences must be determined for each individual case,because they vary with the design and utilization of the building.

As an example it can be mentioned that, if the temperature for thereturn air is higher than the temperature for the outdoor air, theconduit 26 can be closed so that the return air flows directly to theambient while only outdoor air is supplied to the roof structure via theconduit 25 and the fan 23.

As regards the air conditioning unit 5 may be added, that this unit maycomprise e.g. a heat exchanger of a suitable type, for example aregenerative heat exchanger or a recuperative one. In such operationcase when a recuperative heat exchanger is connected in series with theroof structure (gap and ducts), the following advantages are obtained:

(1) Higher total efficiency degree;

(2) Downward adjustment of the liquid flow in the air heat exchanger fordefrosting the exchanger is not required;

(3) Anti-freeze addition in the form of glycol can be reducedsubstantially, thereby yielding an improved heat transfer, which resultsin a higher efficiency degree because no downward adjustment isrequired.

In the foregoing, an imagined embodiment of the invention has beendescribed with reference to a preferred roof structure for carrying outthe invention. As already pointed out, the invention can be applied toother roof structures, provided that an air flow according to theinvention can be established. The two important criteria, thus, are thata gap exists between the covering layer and the carrying roof plate, andthat said plate includes air ducts. The air shall be passed through thegap and through the ducts for further treatment. The invention alsocomprises the inverted flow path. The operation cases described fallwithin the scope of the invention, and in specific cases additionaloperation cases can be imagined. Such a specific operation case occurswhen the roof plate consists of a sheet metal plate 30 (FIG. 10) with aribbed cross-section, the lower surface of which at least partially iscovered with a building slab 31 with high heat storage capacity. Theducts 9 are formed between the slab and the lower surface of the plate.Said slab may consist in known manner of polymer concrete havingincluded therein a salt mixture based on borax and "molten silicic acid"with a suitably balanced melting temperature, about 23° C. The roofplate is shown in FIG. 10. The operation case in this embodimentoccurring arises in the night after operation case 1 and 2, and thesystem is so operated that the indoor air is taken through the heatstoring part of the roof, whereby a very active and efficient heatstoring function is obtained. In this operation case, thus, a connectionis opened between the inside air and the heat storing part of the roofand at the same time the connection between the heat storing part of theroof and the air gap is closed.

We claim:
 1. An arrangement for air condition control of buildings ofthe type having a roof constructed of self-supporting roof plates havingsubstantial mass and a relatively wide span, and a covering layersupported on the outside of the roof plates to provide an air gapbetween said roof plates and said covering layer for passing airtherethrough, comprising ducts formed in said roof plates, an opening inone end of said ducts, an air conditioning unit, air intakes connectedto the interior of the building, means for connecting said opening tosaid air conditioning unit and to said intakes, and one or more upwardconnecting means connecting said ducts to said air gap locatedthereabove.
 2. An arrangement as defined in claim 1 wherein pass-overconduits are provided for connecting the ducts of several plates inseries one after the other.
 3. An arrangement as defined in claim 2wherein said pass-over conduits have an opening comprising said upwardconnections.
 4. An arrangement as defined in claim 1 wherein said upwardconnections between said ducts and said air gap are of a number anddesign to provide a substantially uniform air flow in the gap.
 5. Anarrangement as defined in claim 1 wherein means are provided for airexchange between the gap and the atmosphere comprising a venting devicelocated in the ridge of the roof, said gap being closed at the guttervalleys on the edge of the roof.
 6. An arrangement as defined in claim 1wherein said ducts have transverse connections with ducts of theadjacent roof plate.
 7. An arrangement as defined in claim 1 whereinsaid roof plates comprise concrete elements with TT-shapedcross-section, and said ducts are provided in substantially every beamweb of each concrete element.
 8. An arrangement as defined in claim 1wherein said roof plates each comprise a plate having a ribbedcross-section, the lower ribbed surface of which at least partially iscovered with a building slab with high heat storage capacity, so thatsaid ducts are formed between said lower surface and the building slab.